To demonstrate the basic difference in wave propagation of 900 MHz and 2.4 GHz waves, a quick look at path loss is provided. As waves propagate out from the transmitter, some attenuation of the signal takes place due to properties of the medium (air in most cases). Path loss describes this attenuation as a function of the wavelength of the operating frequency and the distance between the transmitter and receiver. Path loss is derived from the Friis transmission equation and is defined as:

Path Loss = 20 log(4*p*r/λ) dB
where r is the distance between the transmitter and receiver, and λ is the wavelength . The table below shows how path loss differs between 900 MHz transmitters (λ=0.33 meters) and the 2.4 GHz transmitters (λ=0.125 meters).

NOTE: Path loss analysis does not account for effects such as differing TX power outputs and RX sensitivities. See the "Range of 9XStream (900 MHz) and 24XStream (2.4GHz) Modules" section at the bottom of this page for more detailed range information.

R = 10 Meters

R = 1000 Meters

900 MHz
51.527 dB
71.527 dB

91.527 dB

2.4 GHz
60.046 dB
80.046 dB

100.046 dB

Thus, the path loss is +8.519dB more over a given range for the 2.4 GHz modules. Since the range doubles with every 6 dB of reduced path loss, the 900 MHz modules have 2.67 times as much range as the 2.4 GHz modules [2^(8.519/6) = 2.67].

Range of 9XStream (900 MHz) and 24XStream (2.4 GHz) Modules
A link budget analysis can mathematically predict the system range based on the power output, receiver sensitivity, antenna gains, path loss, and fading margin.

The path loss equation represents path loss (signal attenuation) as a function of distance between the receiver and transmitter and the wavelength of the operating frequency. This equation is derived from the Friis transmission equation and is given by: